An example of a check valve provided with a guide member for guiding a valve element in an axial direction of an annular valve seat is disclosed in Japanese Published Unexamined Patent Application No. Hei 10-30743. In this check valve, an inlet, a valve chest having a diameter larger than that of the inlet, and an outlet are formed in a valve casing, an annular valve seat is formed between the inlet and the valve chest, a valve element for opening and closing the annular valve seat is disposed within the valve chest, a valve stem is projectingly provided on the inlet side of the valve element, ribs projecting from an inner wall of the inlet are formed within the inlet, and at inner ends of the ribs is formed a guide member with which an outer periphery of the valve stem is in sliding contact.
In the above conventional check valve, since the ribs with the guide member formed at the inner ends thereof are positioned within the inlet, there has been the problem that a fluid passing area around the ribs and the guide member is small and that therefore the flow rate is small.
Taking note of the above problem of the prior art, the present invention, as a technical object thereof, aims at providing a check valve which permits a large flow rate by increasing the fluid passing area around the ribs and the guide member.